A game by Fabraz for PC, Mac, Linux, PS4, Xbox One, and Switch, originally released in 2017.
In Slime-san, you take on the role of a simple green slime who is swallowed up by a giant worm while he is wandering through the forest. Once within the worm’s gullet, Slime-san jumps, dashes, and slimes his way through hundreds of 5-color pixelated platforming environments that are set in different parts of the worm’s long body. Starting at the worm’s hind end and working his way forward, Slime-san must outrun walls of constantly-rising stomach acid as he fights to find a way out.

The game’s premise is a bit odd – although it is certainly in line with some of the strange stories of the 8- and 16-bit days – which lends itself to some absurd situations. For instance, the slime encounters numerous other characters within the worm who have been similarly swallowed up, as well as an entire town located within the worm’s intestines. And, while many classic games feature boss fights against oversized body parts, few see the player attempting to take down a giant fully-engorged worm penis.

Slime-san has a 2x nonvariable jump, a multi-directional dash that may be initiated on the ground or in the air, and the ability to wall slide and wall jump quickly up any vertical surface. He can also perform a double jump in a couple of different ways, both of which are nontraditional… First, a double jump may be executed by performing an upward dash, which is somewhat less precise than a traditional double jump, as it requires the player to press UP and DASH, rather than leaving his finger on the JUMP button and simply tapping it again.

The second method involves the small white bird that rides around on Slime-san’s head. As long as the bird is on his head, the player can jump a second time by simply pressing JUMP in midair. However, the bird becomes disconnected from Slime-san whenever he performs a jump or a dash, preventing a standard double jump. But Slime-san can jump again while falling, as long as he walks off a ledge, allowing him to cross gaps and get beneath low overhangs, and he can still perform a dash afterwards.

Finally, the slime has the ability to “morph”, which turns him transparent and allows him to pass through green objects, while simultaneously slowing down time. This allows for more precise movement, but the player must often switch between transparent and non-transparent modes... morphing to pass through green barriers and then un-morphing to land on green platforms.

Mastering all of these techniques is required to survive the game’s whopping 400 levels, which permute upon every possible gameplay mechanic to create new challenges in each area. Just when you think you’ve seen the last nuance to the mechanics, the game throws something entirely new at you. Most levels are single-screen affairs and can be completed by skilled players in 10-15 seconds. Death is fast and frequent, with instant reloads, so it’s possible to die several times and still make it through a level in under a minute.

In addition to the large level count, the game is positively packed with additional content… Each set of four levels has a trophy that can be earned by completing the area under its par time (which is quite low), and there are speedrunning modes with leaderboards. Each level has an optional apple that can be eaten by the slime, and many of these are placed in hard-to-reach locations. These apples act as the game’s currency, allowing players to purchase new characters that each have different playstyles, including changing the player’s movement speed, jump distance, and dash distance, allowing players to further experiment with the game’s basic mechanics. In addition, players can purchase some aesthetic changes to alter the border and the overall look of the game, as well as change the characters’ clothing.

Many levels feature alternate exits that lead to NPC’s in need of rescue, each of whom rewards the player with one coin, and coins can be spent on a variety of arcade games back in town. These arcade games - which also feature multiplayer - offer takes on numerous popular games, including Pong, DOOM, Sega's Ninja, and Super Mario Kart. Once the player finishes the game, a New Game+ mode offers variations on the existing 400 levels for players who truly wish to challenge themselves, and players may take on the Boss Rush mode.

The slime enters each level with one goal: make it to the exit. White objects represent solid ground, red ones are things that will kill you, and green ones represent solid objects that you can pass through by morphing. Each level has a countdown clock in the upper left that indicates how long you have until red stomach acid starts filling the room, along with an arrow that tells you which direction he acid will be coming from. By default, you can see the entirety of the room, but you can also zoom in to see your immediate surroundings.

Things start out simply with the player avoiding red objects and enemies as he hops and wall jumps his way through the levels. Players can dash through cracked blocks to break them and knock solid blocks out of the way or push them into pools of acid to create stepping stones. Players encounter underwater areas where movement is slowed, but they can jump and dash infinitely in order to move more quickly.

There are a number of green critters in the game, which the player can safely pass through by morphing, but sometimes the player needs to interact with these creatures in order to move forward, such as bouncing on the backs of floating turtles, using their shells as trampolines. Per platforming standards, there are a number of bouncy trampoline-like objects, as well as fans that push the player away from them.

Aside from the rising acid that acts as each level’s timer, there are a number of time-based challenges. Some of these involve waiting for blocks to slide out of the way, or waiting for acid to partially fill the room in order to ride floating platforms upward. There are also numerous levels where the player must collect keys to unlock doors for himself and for enemy creatures that activate triggers while they patrol.

Most levels can be beaten very quickly, but some time-based challenges require players to wait a bit before moving forward. This generally adds tension, but there are a handful of poorly-timed challenges that see players simply standing in place while they wait for the path ahead to open, interrupting the game’s otherwise quick pace.

There are several kinds of platforms, covering the typical genre range with moving platforms, falling blocks, slippery surfaces, conveyor belts, and sticky blocks that require the player to jump away from them. The low-rez graphical style occasionally makes it difficult to parse these elements while dashing along at full speed, but the penalty for failure is quite low, allowing players to learn from their mistakes and quickly make another attempt.

Nearly every conceivable platforming staple makes an appearance throughout the lengthy adventure, including teleporters, gravity flipping, Donkey Kong-style rolling barrels, grappling and swinging,
Tetris-style falling block challenges, Q-Bert-style color swapping, increasing and decreasing the slime’s size, etc. While gaming veterans have seen all of these elements before, the morph ability continues to keep things interesting. Players must constantly use the ability in new and increasingly complex ways in order to overcome the game’s challenges.

Some of the more complex morphing challenges include swapping blocks to create safe pathways for yourself (and some enemies) while dealing with enemies and turrets. Sometimes you have to climb up a vertical green surface, morph through it, perform a midair jump, and then un-morph to stick a landing on another green platform or wall. These quick switches are made more difficult by the fact that time slows down while the ability is engaged and speeds back up when disengaged, making it very challenging when you have to switch between modes in rapid succession.

In addition to static single-screen levels, there are a small number of chase sequences where the player must move through a scrolling environment while a wall of acid moves in from the left, requiring speedy reflexes and deft use of the slime’s movement repertoire. These levels are also somewhat longer, thus adding a higher penalty should the player die and have to return to the start. It’s also worth noting that – despite the staggering level count – levels cannot be skipped if the player finds himself having difficulty overcoming a given challenge; each level must be completed before moving on to the next.

The game also features a number of boss encounters, with one appearing after every 20 areas. These bosses take the form of various internal organs, including the aforementioned penis, as well as a heart, a brain, and a grinning uvula. These encounters require the player to make use of all of his skills, but they become fairly easy once he understands the boss’ movement patterns. Bosses are multi-phase affairs with changes to the environment and/or attack patterns with each phase.

2D CREDSlime-san was developed by Fabraz, creators of Planet Diver, Cannon Crasha, and Wild Wild Pixel. The game’s credits include studio founder and designer Fabian Rastorfer, programmer Ben Miller, level designer Edgar Castro, and Sound Designer Britt Brady. The game’s soundtrack includes work from more than a dozen chiptune artists, including Adhesive Wombat, Tiasu, MegaNeko, Kommissar, and Richard Gould.